The present invention relates to butterfly fire dampers for use in air ducts, particularly those which are intended for use as fire, smoke and/or air control dampers and which are intended to automatically move between the open and closed positions in response to the presence of fire or, (when a remotely activatable releasing device is used) in response to the receipt of a fire or smoke activated signal, and/or to be moved to an intermediate position to allow preselected volumes of air therethrough.
Multiple, folding blade fire dampers having a plurality of blades disposed within a frame having an inwardly depending flange are known in the prior art, as for example, in my U.S. Pat. Nos. 3,814,165 and 3,866,657. In my U.S. Pat. No. 3,899,156, a single blade fire damper is described. In this regard, please refer to U.S. Pat. Nos. 3,009,473 (Hennan); 2,148,530; 3,337,991 ( Adams); 3,720,153 (Jardinier et al); French Pat. No. 2,307,228 (Barbarin) and my prior U.S. Pat. No. 3,725,972.
The present invention also relates to the field of operators, and more particularly to the field of damper operators which actuate butterfly dampers in response to heat or remote signals but which are resettable immediately after the passage of activation conditions so that they may again respond to fire conditions. The present invention also relates to operators which are adapted to set the position of a damper's blades to regulate the volume of air passing therethrough under normal conditions. Finally, the present invention relates to such operators which may be reset while providing only limited manual access to the vicinity of the damper blades.
Conventionally, fusible or meltable releasing devices have been employed, such as fusible links in cables which are held under tension in normal conditions and which are activated by the melting of the link and the link break cable to deploy the blades of a fire or smoke damper into their activated positions.
More recently, bimetallic links, such as those illustrated in my previously issued U.S. Pat. Nos. 3,889,314 entitled, "HEAT ACTUATED LINK" and 3,725,972 entitled "FIRE LINK AND METHOD OF ACTUATING SAME" have been described wherein a mounting element having a bimetallic strip attached thereto, which cooperates therewith, may engage a pawl having an aperture therein which is engaged by a bimetallic element in the normal position and which is released thereby as the tip of the bimetallic element separates from the striker portion of the mounting element thereof to release the pawl. These bimetallic links have conventionally been installed by attaching a cable to either the pawl, the mounting element, or both, in a manner similar to that use for the fusible or meltable links described above. These bimetallic links have exhibited certain advantages over the prior art fusible links in that following a return to temperatures, the link may be reset by reinserting the pawl into the remaining link assembly.
Unfortunately, prior art devices of the type described above have usually been installed in butterfly dampers in a manner which prevents those butterfly dampers from being used for volume control purposes. Additionally, such releasing devices have often been located in positions which require complete access to the butterfly damper, and particularly to the remote blade portions thereof where the link is most often located. In certain installations, such as smoke tunnels, ducks, plenums, etc., human access to reset or replace releasing devices is limited. Additionally, relatively skilled personnel must be employed in order to reset or replace the aforementioned releasing devices. In the case of bimetallic links, these people must at least understand the proper method of inserting the pawl so that it is properly gripped by the remaining portion of the link.
For one approach to this problem, please refer to my previously issued U.S. Pat. No. 3,796,248, dated Mar. 12, 1974 entitled, "REMOTELY RESETTABLE FIRE DAMPER".